Your business year-end, not 5 April, is relevant for capital allowances purposes. If however you are running a business and making up accounts to 31 March or 5 April you should consider buying plant and machinery to take advantage of the £1 million Annual Investment Allowance (AIA).
The AIA provides a 100% tax write-off for equipment used in your business. This tax relief extends to fixtures and fittings within business premises such as electrical, water, and heating systems. AIA does not apply to motor cars but there is a special 100% tax relief if you buy a new car that emits no more than 50g CO2 per kilometer. Note however that from April 2021 100% tax relief will only apply where there are zero emissions.